Imaging Systems X-Rays

Imaging Systems: Shared Elements 1.Where did the energy come from? 2.What happens when the energy interacts with matter? 3.How is the energy collected after that interaction? 4.How is the collected energy captured? 5.How is the signal manipulated? 6.What do you do with the information? 7.How is the information shown? 8.How does the brain interpret that information?

Source X rays are a form of electromagnetic radiation. They have enough energy to liberate electrons from the atoms that bind them  ionizing radiation. X rays can be produced by different methods: Synchrotron, free electron lasers, x-ray tubes that emit bremsstrahlung and characteristic x rays. MRI PET scan Film photography Digital photography Television VCR DVD Microscopes Telescopes CRT LCD Plasma display Thermal imagers Passive IR sensors Radar Movies Overhead projector Slide projector Holography Copiers Scanners Printers (inkjet) Printers (laser) Printing (lithography) Printing (screen) Printing (intaglio) Aerial imaging Astronomy Airborne telescopes Orbiting telescopes Satellite imaging CCD CMOS Color cameras Color displays Computer vision Robotic vision Nightlight Image compression Human visual system Glasses Ultrasound Contact lenses Laser surgery … 1. “Where did the energy come from?”

MRI PET scan Film photography Digital photography Television VCR DVD Microscopes Telescopes CRT LCD Plasma display Thermal imagers Passive IR sensors Radar Movies Overhead projector Slide projector Holography Copiers Scanners Printers (inkjet) Printers (laser) Printing (lithography) Printing (screen) Printing (intaglio) Aerial imaging Astronomy Airborne telescopes Orbiting telescopes Satellite imaging CCD CMOS Color cameras Color displays Computer vision Robotic vision Nightlight Image compression Human visual system Glasses Ultrasound Contact lenses Laser surgery … Energetic electrons may be attracted into partial orbit around the nucleus of a target atom. They slow down, losing kinetic energy. The energy lost is converted into a photon of electromagnetic radiation, called bremsstrahlung radiation. The energy lost by the incoming electron may be of any amount, up to the total kinetic energy carried by the electron. Similarly, the photon emitted may have any value up to the total kinetic energy of the electron. Source

MRI PET scan Film photography Digital photography Television VCR DVD Microscopes Telescopes CRT LCD Plasma display Thermal imagers Passive IR sensors Radar Movies Overhead projector Slide projector Holography Copiers Scanners Printers (inkjet) Printers (laser) Printing (lithography) Printing (screen) Printing (intaglio) Aerial imaging Astronomy Airborne telescopes Orbiting telescopes Satellite imaging CCD CMOS Color cameras Color displays Computer vision Robotic vision Nightlight Image compression Human visual system Glasses Ultrasound Contact lenses Laser surgery … e1e1 e2e2 e3e3 E1E1 E2E2 E3E3 Source

Object 2. “What happens when the energy interacts with matter?” MRI PET scan Film photography Digital photography Television VCR DVD Microscopes Telescopes CRT LCD Plasma display Thermal imagers Passive IR sensors Radar Movies Overhead projector Slide projector Holography Copiers Scanners Printers (inkjet) Printers (laser) Printing (lithography) Printing (screen) Printing (intaglio) Aerial imaging Astronomy Airborne telescopes Orbiting telescopes Satellite imaging CCD CMOS Color cameras Color displays Computer vision Robotic vision Nightlight Image compression Human visual system Glasses Ultrasound Contact lenses Laser surgery … Interaction between X rays and matter usually results in the deposition of energy. Different types of interactions include: Photoelectric effect, Rayleigh scattering, Compton scattering, pair and triplet production. These mechanisms combine to produce attenuation of the incident x-ray photon beam as it passes through matter.

Object MRI PET scan Film photography Digital photography Television VCR DVD Microscopes Telescopes CRT LCD Plasma display Thermal imagers Passive IR sensors Radar Movies Overhead projector Slide projector Holography Copiers Scanners Printers (inkjet) Printers (laser) Printing (lithography) Printing (screen) Printing (intaglio) Aerial imaging Astronomy Airborne telescopes Orbiting telescopes Satellite imaging CCD CMOS Color cameras Color displays Computer vision Robotic vision Nightlight Image compression Human visual system Glasses Ultrasound Contact lenses Laser surgery … Penetrate Scatter Compton interaction Photoelectric interaction Release kinetic energy

Collection and Detection 3. “How is the energy collected after that interaction?” MRI PET scan Film photography Digital photography Television VCR DVD Microscopes Telescopes CRT LCD Plasma display Thermal imagers Passive IR sensors Radar Movies Overhead projector Slide projector Holography Copiers Scanners Printers (inkjet) Printers (laser) Printing (lithography) Printing (screen) Printing (intaglio) Aerial imaging Astronomy Airborne telescopes Orbiting telescopes Satellite imaging CCD CMOS Color cameras Color displays Computer vision Robotic vision Nightlight Image compression Human visual system Glasses Ultrasound Contact lenses Laser surgery … There are two basic ways to create x-ray images: a)Pass an x-ray beam through a body section and project a shadow image onto a receptor. b)Computer tomography: use a computer to reconstruct an image from the penetration data.

Detection 4. “How is the collected energy captured?” MRI PET scan Film photography Digital photography Television VCR DVD Microscopes Telescopes CRT LCD Plasma display Thermal imagers Passive IR sensors Radar Movies Overhead projector Slide projector Holography Copiers Scanners Printers (inkjet) Printers (laser) Printing (lithography) Printing (screen) Printing (intaglio) Aerial imaging Astronomy Airborne telescopes Orbiting telescopes Satellite imaging CCD CMOS Color cameras Color displays Computer vision Robotic vision Nightlight Image compression Human visual system Glasses Ultrasound Contact lenses Laser surgery … In conventional radiography the receptor consists of the film mounted in contact with an intensifier screen. The contrast that appears in the image is determined by several factors: penetration characteristics, scattered radiation, contrast characteristics of the film.

Processing 5. “How is the signal manipulated?” MRI PET scan Film photography Digital photography Television VCR DVD Microscopes Telescopes CRT LCD Plasma display Thermal imagers Passive IR sensors Radar Movies Overhead projector Slide projector Holography Copiers Scanners Printers (inkjet) Printers (laser) Printing (lithography) Printing (screen) Printing (intaglio) Aerial imaging Astronomy Airborne telescopes Orbiting telescopes Satellite imaging CCD CMOS Color cameras Color displays Computer vision Robotic vision Nightlight Image compression Human visual system Glasses Ultrasound Contact lenses Laser surgery … a) The most important effect of the intensifying screens on image quality is that they blur the image. b)Motion blur c) Finite size of x-ray tube focal spot

Processing MRI PET scan Film photography Digital photography Television VCR DVD Microscopes Telescopes CRT LCD Plasma display Thermal imagers Passive IR sensors Radar Movies Overhead projector Slide projector Holography Copiers Scanners Printers (inkjet) Printers (laser) Printing (lithography) Printing (screen) Printing (intaglio) Aerial imaging Astronomy Airborne telescopes Orbiting telescopes Satellite imaging CCD CMOS Color cameras Color displays Computer vision Robotic vision Nightlight Image compression Human visual system Glasses Ultrasound Contact lenses Laser surgery … 5. “How is the signal manipulated?” If the image is stored in computer memory processing for noise reduction is possible. Contrast can be manipulated. Images may be subtracted form each other to show a difference or change between them.

Compression/Storage/Transmission 6. “What do you do with the information?” MRI PET scan Film photography Digital photography Television VCR DVD Microscopes Telescopes CRT LCD Plasma display Thermal imagers Passive IR sensors Radar Movies Overhead projector Slide projector Holography Copiers Scanners Printers (inkjet) Printers (laser) Printing (lithography) Printing (screen) Printing (intaglio) Aerial imaging Astronomy Airborne telescopes Orbiting telescopes Satellite imaging CCD CMOS Color cameras Color displays Computer vision Robotic vision Nightlight Image compression Human visual system Glasses Ultrasound Contact lenses Laser surgery … In conventional radiography hospitals store films In digital radiography images are stored in computer memory. Image files may be compressed for transmission.

Display 7. “How is the information shown?” MRI PET scan Film photography Digital photography Television VCR DVD Microscopes Telescopes CRT LCD Plasma display Thermal imagers Passive IR sensors Radar Movies Overhead projector Slide projector Holography Copiers Scanners Printers (inkjet) Printers (laser) Printing (lithography) Printing (screen) Printing (intaglio) Aerial imaging Astronomy Airborne telescopes Orbiting telescopes Satellite imaging CCD CMOS Color cameras Color displays Computer vision Robotic vision Nightlight Image compression Human visual system Glasses Ultrasound Contact lenses Laser surgery … In conventional radiography the image is a photographic film. Digital radiography can be displayed in either a CRT monitor or a laser film printer. But these are not able to display full dynamic range. One way to overcome limitations is to use image processing techniques to enhance lesion visibility.

Perception 8. “How does the brain interpret that information?” MRI PET scan Film photography Digital photography Television VCR DVD Microscopes Telescopes CRT LCD Plasma display Thermal imagers Passive IR sensors Radar Movies Overhead projector Slide projector Holography Copiers Scanners Printers (inkjet) Printers (laser) Printing (lithography) Printing (screen) Printing (intaglio) Aerial imaging Astronomy Airborne telescopes Orbiting telescopes Satellite imaging CCD CMOS Color cameras Color displays Computer vision Robotic vision Nightlight Image compression Human visual system Glasses Ultrasound Contact lenses Laser surgery … Human observers are integral part of imaging system. Relationship between physical image quality and diagnostic performance is known as psychophysics. Use of ROC (receiver operating characteristics) is one of the major statistical analytical tools to characterize human performance.

The “Imaging Chain” The common thread in these imaging systems can be described in terms of the component ‘black boxes’ that make them up. 1.Source 2.Object 3.Collection 4.Detection 5.Processing 6.Compression/storage/transmission 7.Display 8.Perception